Banned cancer-causing chemicals once used for firefighting has been found in the pups of endangered Australian sea lions at Seal Bay, as well as fur seals in Victoria.
The chemicals Per- and polyfluoroalkyl substances or "PFAS" were detected in juvenile animals and in an adult male.
There was also evidence of transfer of the chemicals from mothers to newborns.
The finding represents another possible blow to Australian sea lions' survival.
Hookworm and tuberculosis already threaten their small and diminishing population, which has fallen by more than 60 percent over four decades.
The new research - part of a long-term health study of seals and sea lions in Australia - identified the chemicals in animals at multiple colonies in Victoria and South Australia from 2017 to 2020.
Where the chemicals have come from is not known, according to Dr Rachael Gray, from the University of Sydney.
"The source to the sea lions is most likely through their diets. For pups, which were all maternally dependent at the time of sampling, this means they are receiving PFAS through gestation and lactation. As such, the geographical foraging areas of the mums is likely important," she said.
Dr Gray returned to Seal Bay this week for more research and more sampling trip for the ivermectin treatment trial to treat hookworm.
Better news is there's been no more cases of the disease tuberculosis detected, and date there have been 227 pups born as we approach the close to the end of the pupping season.
The small sea lion population size increases the species' risk of catastrophic disease impact. Hookworm infection provides an existing disease pressure for the Australian sea lion.
Further, recovery from a significant disease impact would be limited by the species' low reproductive rate.
About 82 percent of pup births occur in South Australia, where there is dependence on just eight large breeding colonies, including Seal Bay.